Plans for a UK trial of the brother of the Manchester Arena suicide bomber are under way as extradition proceedings remain ongoing, say police.

The head of the North West Counter Terrorism Unit, Assistant Chief Constable Russ Jackson of Greater Manchester Police, would not be drawn on the progress of the extradition application made more than six months ago to Libya where Hashem Abedi is currently in custody.

But as a team of about 100 investigators continue to work full-time on the live murder investigation, Mr Jackson told reporters: “We are preparing for a trial.”

Both brothers travelled to Libya in April 2017, before Salman, 22, returned alone before carrying out the attack on May 22 which left 22 dead and hundreds injured.

Hashem Abedi, 21, is understood to be currently held by a militia group in Libya.

A warrant for his arrest in relation to questioning over allegations of murder, attempted murder and conspiracy to cause an explosion was also issued before the extradition request was handed to Libya on November 1 last year.

CCTV image issued by Greater Manchester Police of Salman Abedi on the night he carried out the Manchester Arena terror attack (GMP/PA)

Mr Jackson told reporters that it was “really difficult” to provide any further detail of the extradition process.

He said: “Firstly we must respect the Libyan legal process and we are very grateful to them for considering our request.

“Secondly, it is vital that the court process is respected in this country and especially the right to a fair trial.

“It is because of this that we cannot comment on any specific detail of the case.

Floral tributes to victims of the Manchester bombing (Ben Birchall/PA)

“When we can say more, we will of course do so.

“In the meantime we will continue to gather evidence, searching for as much detail about what happened and evidence of anyone responsible whilst supporting the families, many of whom are going through unimaginable pain.”

Part of the ongoing inquiry was an extensive search of 11,000 tonnes of rubbish at a landfill site in Bury which finished last week and failed to uncover any trace of a large blue suitcase which the bomber was seen on CCTV pulling in Manchester city centre on May 22, although not believed to have been used in the explosion.

Mr Jackson said they had now established that more than 800 people suffered physical and psychological injuries from the bombing.

He said: “Over the past year the investigation team has worked hard to support those affected and we are consistently moved by the grace and dignity they show in trying to repair their lives.

“Of course for many the loss is too great for them to ever make a full recovery from this terrible event.”

He said the dedicated team of 100 officers continue to piece together evidence as they interview witnesses, painstakingly watch thousands of hours of CCTV and analyse forensic material in an investigation which has cost, so far, about £4 million.

More than 2,000 witness statements have been taken along with the seizure of more than 13,000 exhibits and the examination of 16 terabytes of data.

Manchester Arena was the scene of the attack by Salman Abedi (Peter Byrne/PA)

Police have previously said they do not think Salman Abedi was part of a wider network but believe others were involved in the planning of the attack and named Hashem as a suspect.

Salman Abedi’s bomb has been described as “substantial” in size, and he had put it inside a tin with the shrapnel, nuts and bolts, placed around it.

He detonated the device at the end of an Ariana Grande concert with 353 people, including 175 children, around him in the foyer of the venue.

The Abedi family, originally from Libya, fled during the Gaddafi dictatorship with his father returning to fight with opposition forces when the uprising began in 2011.

An extradition agreement between the UK and Libya had been agreed in 2009 but since the overthrow of Gaddafi the country has been split into warring factions with the United Nations-backed, internationally recognised Government of National Accord (GNA) struggling to assert control over swathes of the country in the hands of dozens of different militias including Isis-affiliated groups.